[xsd gen] Enhance xsd_serialize function

Clearer handling of entities, drop case of date/datetime (we may only have bool
or string final values).

entities/profile_generation.py

@@ -16,7 +16,6 @@
 """cubicweb-seda entity's classes"""
 
 from collections import defaultdict
-from datetime import date, datetime
 
 from lxml import etree
 from pyxst.xml_struct import graph_nodes
@@ -353,21 +352,17 @@ def xsd_serialize(value):
     """Return XSD value as a string depending on the type of the given `value`."""
     if value is None:
         return None
-    if hasattr(value, 'labels'):
-        # value is a Concept
-        return value.labels['en']
-    if hasattr(value, 'id'):
-        # value is something in the profile which has a id
-        return value.id
     if hasattr(value, 'eid'):
+        if value.cw_etype == 'Concept':
+            return value.labels['en']
+        if hasattr(value, 'id'):
+            # value is something in the profile which has a id (e.g. archive unit, data object)
+            return value.id
         return None  # intermediary entity
     if isinstance(value, bool):
         return 'true' if value else 'false'
-    if isinstance(value, (date, datetime)):
-        return value.isoformat() + 'Z'
-    # if isinstance(value, Binary):
-    #     return b64encode(value.getvalue)
-    return unicode(value)  # XXX
+    assert isinstance(value, basestring), repr(value)
+    return unicode(value)
 
 
 def xsd_element_cardinality(occ, card_entity):